The PIMM Force Field - Recent Developments

Abstract

Even though the steady advances in computing power and algorithms continue to increase the competition by semiempirical and ab initio methods, they also serve to open new realms for modern force fields. Among the key advantages of the classical molecular mechanics approach is their ability to handle systems with a large number of atoms and degrees of freedom. A second and increasingly important feature lies in the fact that they can often provide a simple but efficient means of modeling metal complexes. In recent years, our PIMM force field [1] for organic molecules has found successful application in a number of problems in organic and bio-organic chemistry. Examples range from peptide complexes of alkaline earths cations to porphyrin complexes of the transition metals. In its traditional field, the conformational analysis of organic molecules, satisfying results have been reported especially for carbohydrates [2]. Besides conventional energy minimization techniques and systematic permutations, molecular dynamics calculations have gained increasing importance. In its current form, the program fills the niche between the small-molecule force fields and the protein modeling packages. Even on the pc platform, systems of up to 2000 atoms can readily be studied without simplifications. This entails not only an all-atom representation, but also a semiempirical SCF calculation of the pi electrons and a Hessian matrix-based optimization algorithm. Current projects address the specific continuum effects in condensed phases, i.e. a model representation of solvent and packing effects.